What it usually means
Something specific is missing. Either the person saying this does not know what it is, or they are not in a position to say. Both are worth finding out, and neither is answered by waiting.
Promotion decisions are often settled in a room you are not in. "Not ready" can be your manager relaying a verdict they argued against.
What else it can mean
- A missing piece of evidence. There is a thing they need to have seen, and have not.
- A room above your manager. Your manager made the case and lost it, and "not ready" is the version that can be repeated.
- A queue. Someone else is ahead this cycle and the reason is timing, not you.
What to find out first
Whose decision it was, and what would have changed it. If the answer is "the committee", find out when it next sits.
What the research says, and where it stops
In one organisation’s calibration committees, about a quarter of initial ratings were adjusted, most of them downward. Ratings of employees further from the committee in the hierarchy were less likely to be changed at all.
Demeré, Sedatole & Woods 2019, Management Science 65(4). Limit: One organisation, one function (internal audit), 2007–2009. That your company works this way is an inference.
Which door
This is The Ladder — “I asked what's holding back my promotion. The answer is always vague.”